Reuters, DHAKA - Political parties largely silenced by a state of emergency are now sounding a chorus of demands for release of detained leaders as Bangladesh prepares to mark its independence anniversary this week.

At least one party threatens demonstrations if former prime minister Sheikh Hasina is not released before the March 26 anniversary, and corruption charges against her quashed.

"If that does not happen, the Awami League (Hasina's party) would defy all bans and launch protests against the illegal jailing and (urge) bringing her out, along with other party leaders," Tofayel Ahmed, a former minister and senior Awami leader, told reporters.

He said the senior leaders and top policy planners of the party met late on Sunday in Dhaka to review the situation, and warned they might "not be able to hold back a people's upsurge to free Hasina and her comrades".

His senior colleague Abdur Razzak said refusing Hasina a parole for having treatment of her ailing ears in the United States was "illegal, unacceptable and a denial of justice".

Khaleda Zia supporters also demanded her release from jail before March 26, in a letter addressed to President Iajuddin Ahmed. "Set her free immediately.

We all are waiting for her and her instructions to break the impasse" over emergency and related restrictions, said Rizvi Ahmed, a senior leader of Khaleda's Bangladesh Nationalist Party (BNP).

Hasina and Khaleda alternated as prime ministers of impoverished and disaster-prone Bangladesh for 15 years until October 2006, and could be key contenders for power in future elections.

Bangladesh's army-backed interim government, which took over in January 2007 following months of political violence, put the country of 140 million people under an indefinite state of emergency.

It banned political activities and launched a massive crackdown on allegedly corrupt politicians, but vowed to hold a free, fair and credible parliamentary election before this year-end.

The anti-corruption drive netted more than 170 key political figures including Khaleda's two sons, Hasina's relatives and dozens of their former ministers.

If convicted they will be barred from contesting the polls. Not all have been put on trial yet, but their parties want them tried in normal civil courts, not special courts under emergency powers.

"Our leaders have been held deliberately to keep that away from the polls, but people still love them," acting Awami chief Zillur Rahman said late on Sunday.

Hasina is suffering from high blood pressure, allergy and eye and ear problems, and is in a hospital in Dhaka. She has asked for access to treatment, especially for hearing impairment, in the United States where her children live and she had been treated earlier.

Khaleda, suffering from arthritis and related complaints, told followers through her attorneys she would not go abroad for healthcare.